Not Applicable
Currently, there are three types of communication networks that extend throughout the United States: the telephone networks, the collection of data networks that make up the Internet, and the cable television networks. These groups of networks are not integrated with each other, but are not entirely separate. Although the telephone networks were designed for voice, they can handle data communications and limited video (e.g., video phone and video teleconferencing). Similarly, the Internet and the cable networks, which were designed for data and video, respectively, can accommodate to some extent voice, data, and video. Over the long term, it is not beneficial to maintain three groups of non-integrated networks. Instead, there should be an integrated network that can handle all communications functions. Advances in communications technology, particularly fiber optic technology, make this goal feasible.
Data rates of greater than 1 terabit per second (Tb/s) over a single optical fiber have been demonstrated experimentally. In one case, a single fiber carried 126 wavelength division multiplexed (WDM) channels each modulated at 20 Gb/s. Fiber optic systems that can support terabit-per-second data rates and over 100 WDM channels are expected to become commercially viable within the next several years. With these capabilities, it is possible to construct networks that can accommodate extremely high data rates. A network architecture designed to exploit fiber optic capabilities would be significantly different, and much simpler, than the architectures of current networks.
The rationale for an integrated services digital network (ISDN) is to support various communication functions, including voice, data, and video on a single integrated network. Narrowband ISDN (N-ISDN) supports subscriber data rates up to Txe2x88x921 rates (1.5 Mb/s) using existing twisted pair access lines. With broadband ISDN (B-ISDN), the goal is to provide subscriber data rates of 155 Mb/s and higher. This aggressive goal requires the fuller exploitation of the capabilities of fiber optic communications technology.
An architecture is presented for a wide-area B-ISDN fiber optic network capable of covering the United States and providing a 155 Mb/s data rate for all U.S. subscribers. A data rate of this magnitude is more than enough to support current voice, data, and video requirements and retain capacity for future growth. In the proposed network architecture, the extremely high fiber capacity is exploited by multiplexing many subscriber signals on a single fiber. This allows the number of subscriber access lines and the number of switching centers in the network to be greatly reduced compared to current networks. Along with fiber capacity, the large number of possible WDM channels on a fiber can be exploited to construct an optical backbone network that interconnects network switching centers.
The disclosed network provides an STM-1 (155 Mb/s) interface for each subscriber in the U.S., which would support multiple voice, data, and video channels. The proposed network can provides all the features of the current telephone, Internet, and cable TV networks, with sufficient excess capacity to support future applications.
Signals from several thousand subscribers are multiplexed on a single fiber pair connected to an intelligent switching center. With this approach, telephone central offices (COs) become multiplexing centers rather than switching centers, and the number of switching centers required to cover the nation can be greatly reduced. With the proposed architecture, on the order of 500 switching centers are interconnected by an optical backbone. Physical layer connections are established through the backbone between each pair of switching centers. Multiple ATM connections are carried within each physical layer connection.
The backbone is divided into optical network segments such that each segment covers approximately xe2x85x9 of the contiguous United States. An integral number of space-wavelength channels are assigned to each connection through a network segment, with each of these connections containing many end-to-end subscriber connections. Space-wavelength channels are switched intact by the network segment, which simplifies signal processing and facilitates operation at extremely high data rates.
Achieving the full STM-1 data rate requires running optical fiber to the subscriber premises. However, a useful broadband capability can be achieved in the near term using Asymmetric Digital Subscriber Loop (ADSL) technology, in conjunction with existing twisted pair subscriber access lines.
The proposed broadband network can be extended beyond the borders of the contiguous United States. Eventually the network can be expanded into a global network.